People often ask me what to wear in order to be comfortable riding a bicycle in temperatures that could freeze boiling water before it hit the ground. The quick answer is, “quite a lot.” But it’s not as simple as that. Bike riders cannot simply wedge themselves into every article of clothing they have in their closets and expect good results. There is definitely a science to it. And like any modern science, truth is forged in the fire of trial and error, and subjects nearly always emerge with theories of their own.

Here are the “truths” I’ve discovered:

The first rule in dressing for dangerously cold: Layer, layer, layer. This is the most important rule, and yet it is the hardest one to quantify. Too many layers will leave a cyclist soaked in sweat. Too few will invite in the Arctic wind. The point of layering is to be constantly vigilant of how you’re feeling, and adding and subtracting articles of clothing as necessary. I like to use fleece jackets and have found that the number I need is directly proportional to the drop in temperature by a ratio of 1:20. One jacket is comfortable when it’s 30 degrees. Two when it’s 10. Three when it’s 10. And so on.

The second rule in dressing for the dangerously cold: Cotton kills. Lycra clad cyclists have known this all along. But what many don’t know is, cotton really kills. It soaks up its own weight in sweat, which quickly converts to ice, and the resulting solid frost armor is worse than useless when it comes to insulation. So instead, I use a skin tight, sweat wicking polypro base layer on my legs and torso, then the aforementioned fleece layers (which also repel water toward my outer shell). The outer shell has plenty of ventilation to hopefully send that sweat skyward. Anything that solidifies on clothing is there to stay, which gives a whole new meaning to gaining unwanted weight.

The third rule in dressing for the dangerously cold: Hands and feet first. Never ignore hands and feet, and never underestimate the gear needed to cover them. Layering up socks doesn’t work because toes need room to circulate the warm blood that keeps them toasty and not frostbitten. I use a polypro liner sock followed by something called a vapor barrier layer, which is similar to a durable plastic bag. It keeps all the moisture locked inside, where it can’t find its way into places where it will likely become ice. On top of that is a thick wool sock, winter boots that are three sizes to large for me, and a waterproof overboot. Hands stay the warmest when wrapped in liner gloves, which are then wrapped in mittens, which are then wrapped inside a handlebar mitt that cyclists call a “pogie.” The problem with hands is they become rather useless in all this gear, like awkward stumps with vaguely functional appendages. Once winter cyclists learn to feed themselves with mittens, they know they’re set.

The fourth rule of dressing for the dangerously cold: You really can’t put too much stuff on your head. Others might disagree. But I think two face masks and four hats, or anything else that makes a person look like a bulbous mushroom, are perfectly acceptable.

There are other rules for dressing in the cold. Wearing a down jacket is a good idea. Dry shoes are crucial. And remember, if the glove doesn’t fit, fingers will freeze in it. I’m probably missing several dozen important truths. But I know if I at least remember the first four, I’m off to a good start.